Well this is a first for me.

[Cat_Driver]

Normally after any diesel oil change the new fresh oil I put in is instantly BLACK even when I just check the oil
for the proper amount while refilling the engine.

Last week I changed the oil min, my Excavator, after seeing the very thin viscosity oil the dealer had in the unit when I purchased it used. I replaced their oil with my favorite 15/40 oil mostly because of the temps here( been 117 - 122 all weel). Anyway, after running the machine for 10 hours in brutal conditions, I checked the oil and to my surprise, the oil was about as clean as when I put it it in. I did the old rub it between my finger "test" for viscosity and it was nice and thick unlike what I replaced which was as thin as hydraulic fluid.

Like I said that's a first for me not seeing JET BLACK engine oil in a diesel. I don't know is it the Yanmar technology in the TB260, because my Mercedes Sprinter ALWAYS had black as coal looking oil even after a change. Same with Ford GM, Hino, etc.

 

[Bird]

Yep, I, too, expect oil from a diesel engine to be black.

 

[4570Man]

You can still see the stick through the oil after running all last season plus this season on my 2500 hour Kubota diesel mower. I was running a new 100 hp Kubota skid steer a couple years ago and even past the 100 hour mark the oil was pretty clean looking.

 

[Big Barn]

You didn’t mention if the favorite oil you use is convention or synthetic.

If the oil in your used machine seemed to have thin viscosity it might have been synthetic oil. I believe once you switch to synthetic oil you should stick with it and not revert to conventional.

 

[Cat_Driver]

You didn’t mention if the favorite oil you use is convention or synthetic.

If the oil in your used machine seemed to have thin viscosity it might have been synthetic oil. I believe once you switch to synthetic oil you should stick with it and not revert to conventional.

ON PURPOSE. 4 things a man should never talk about. The oil he uses, politics, religion, or pickup truck to buy. Any of these has the potential of getting a thread shut down. I was on a binge once long ago testing a dozen of the best and some off-brans designer oils and settled on the one I'm using now.


What I can say though I've used the same brand gas and diesel oil for 40 years and the same diesel oil in all my types of diesel since the 80's so it's definitely engine related as opposed to oil-related.

Reading the internet since it was invented I don't think more things get people riled up than lubrication. I don't know what that is?
For me, I can generally feel the difference in oil, and even mentioning that to people hs caused a battle in the past.

I'm to the point now that whatever oil you have been using and working for you is the best oil for you and what's been working for me is the best for me.

 

[Rebeldad1]

did you check the factory specs for replacement oil first?
15/40 doesnt seem to come up much anymore.

 

[LouNY]

We have one diesel on the farm that was one of the early common rail engines,
but it does not have any other pollution equipment on it such as an EGR.
That engine is in a CIH PUMA 125 and that oil will stay clean looking for better then a 100 hours,
an almost identical tractor is the NH T6050 except for the mechanical injection pump it also has no EGR or anything similar,
but the oil in that will be black in a days running. All the other older mechanical pumped diesels also get dirty looking very fast.
My 2015 PU with the diesel the oil gets dirty looking almost as soon as it gets in the engine,
but people that have deleted the EGR report the oil staying clean looking for a considerable time.

 

[Captain Dirty]

I am neither an automotive engineer nor a lubrication chemist, so what follows is purely speculation.

Start with the premise that the black color is bits of "dirt" in the oil. The more dirt that gets left behind after an oil drain, the more dirt is there to contaminate the new oil.

1. The engine may be designed differently; passages are sloped to drain more effectively; check valves may be positioned to trap less oil.
2. Lower viscosity (5W/40 vs 15W/40 vs 30) may allow the oil to drain faster and carry more "dirt" with it.
3. The "soap" molecules may bond more tightly to the "dirt" and not "drop" some of the "dirt" leaving it for the fresh molecules in the new oil to pick up.
4. Those "soap" molecules may be formulated to have less "cling" so more of the "dirt" will be carried away.

Oil chemists are the successors to medieval alchemists; plausible hokum is good for marketing.

 

[RoyKing]

It is all carbon black soot, that a bypass filter can remove, I run a 3 micron on my 7.3L ford and long drives will clean the oil back to clear after short runs dirty it.

 

[Cat_Driver]

did you check the factory specs for replacement oil first?
15/40 doesnt seem to come up much anymore.

Ya I'm good - Also I live in extreme conditions for equipment. 120 degrees PLUS ambient temps, so you can imagine how much heat the engine is generating